Syndesmosis: Definition, Fibrous Joints, Structure and Functions

It is defined as a fibrous joint in which two adjacent bones are joined by a strong membrane or ligaments.

This definition also applies to the  distal tibiofibular syndesmosis , which is a syndesmotic joint made up of two bones and four ligaments.

The distal tibia and fibula form the bony part of the syndesmoses and are joined by the distal anterior tibiofibular ligament, the distal posterior tibiofibular ligament, the transverse ligament, and the interosseous ligament.

In these joints, the bone surfaces are in almost direct contact and the bones are joined by the connective tissue in between . Often in these joints, there is no appreciable movement.

Fibrous joints

These are also called synarthrosis or immobile joints and are the strongest joints in your body.

In these joints, the bony surfaces are in almost direct contact. Often in such joints, there is no appreciable movement.

A fibrous joint in which two bones are joined by relatively long collagen fibers. The separation between the bones and the length of the fibers gives these joints more mobility than a suture or gomphosis.

There are especially mobile syndesmoses between the axes of the radius and the ulna, which are joined by a fibrous interosseous membrane. This allows movements such as pronation and supination of the forearm.


The least mobile syndesmoses are those that join the distal ends of the tibia and fibula together, side by side.

The fibers that join bones can be short or long, so the space between the bones in fibrous joints varies from narrow to wide.

There are three types of fibrous joints. A suture is the tight fibrous junction found between most bones in the skull.

In syndesmoses, the bones are further apart, but held together by a strap of fibrous connective tissue called the ligament, a wide sheet of connective tissue called the interosseous membrane.

This type of fibrous joint is found between the axis regions of the long bones in the forearm and in the leg.

Finally, in a gomphosis, the root of a tooth is anchored through a narrow space by the periodontal ligaments to the walls of its socket in the bony jaw in a synarthrosis.

The suture and gomphosis are fibrous joints that do not allow movement between the bones.


The term syndesmosis means “fastened with a band”, (and whose plural is syndesmosis) in this type of fibrous joint the two parallel bones are joined together thanks to the fibrous connective tissue.

The gap between the bones can be narrow, when the bones are joined by ligaments, or the gap between the two can be wide and filled by a wide sheet of connective tissue called the interosseous membrane.

Syndesmoses are located between the bones of the forearm (radius and ulna) and the leg (tibia and fibula).

Fibrous joints tightly bind adjacent bones and thus serve to provide protection to internal organs, strength to body regions, or weight bearing stability.

In the forearm, the large space between the portions of the radius axis and the ulna bones are tightly bound by an interosseous membrane. Similarly, in the leg, the shafts of the tibia and fibula are also joined by an interosseous membrane.

In addition, in the distal tibiofibular joint, the narrow space between the bones is anchored by fibrous connective tissue and ligaments on both the anterior and posterior aspect of the joint.

The tibiofibular syndesmosis is made up of the interosseous membrane and these ligaments together. Syndesmoses located in the forearm and leg, join parallel bones and prevent their separation.

However, a syndesmosis does not prevent all movement between the bones, and therefore this type of fibrous joint is functionally classified as amphiarthrosis.

In the legs, the syndesmoses present between the tibia and fibula bind tightly to the bones, allowing little movement and firmly locking the talus bone holding it in place between the tibia and fibula at the ankle joint.

This feature provides strength and stability in the leg and ankle, which are very important for supporting the body’s weight.

Generally the result of a bone fracture with a break in the interosseous membrane, is damage to a syndesmotic joint, this can cause pain, decrease in the stability of the bones and can also damage the muscles that are attached to the interosseous membrane .

If the fracture site is not properly immobilized with a cast or splint, the contractile activity of these muscles can cause the broken bones to misalign during healing.